Power semiconductor devices typically include a low-doped drift zone across which the blocking voltage drops. Typically the drift zone originates from an epitaxial layer grown on a heavily doped semiconductor base. In-situ doping during the epitaxial growth results in highly homogeneous distribution of the dopants within the epitaxial layer. Since the growth rate of epitaxial layers is about 1 μm per minute, the process is expensive when drift zones exceed a thickness of about 200 μm and more for blocking voltages beyond 2000 V. Therefore, semiconductor wafers for the manufacture of semiconductor devices with high blocking capability are typically obtained by sawing from silicon ingots grown from a localized molten zone. During the floating zone melting process, the growing silicon crystal typically incorporates dopant atoms at comparatively high homogeneity across the length and the diameter of the silicon ingot.
It is desirable to improve the manufacture of power semiconductor devices.